V. N. Shlyaptsev

Saturated high-repetition-rate 18.9-nm tabletop laser in nickellike molybdenum

We report saturated operation of an 18.9-nm laser at 5-Hz repetition rate. An amplification with a gain-length product GL of 15.5 is obtained in the 4d 1S0-4p 1P1 laser line of Ni-like Mo in plasmas heated at grazing incidence with approximately 1-J pulses of 8.1-ps duration from a tabletop laser system. Lasing is obtained over a broad range of time delays and pumping conditions. We also measure a GL of 13.5 in the 22.6-nm transition of the same ion. The results are of interest for numerous applications requiring high-repetition-rate lasers at wavelengths below 20 nm.

Extremely compact soft X-ray lasers based on capillary discharges

Extremely compact high repetition rate soft X-ray lasers based on capillary discharge excitation have demonstrated average powers of a few milliWatt at 46.9 nm, milli-Joule-level pulse energy, peak spectral brightness several orders of magnitude larger than third-generation synchrotron beam lines, and excellent spatial coherence. Examples of the use of a capillary discharge soft X-ray laser in dense plasma diagnostics and laser ablation of materials are summarized.

Numerical studies of transient and capillary x-ray lasers and their applications

During recent months we have continued investigations of many different aspects of x-ray lasers to characterize and improve the source and applications. This work has included temporal characterization of existing laser-heated x-ray lasers under a wide range of pumping conditions. We have also looked into more details at different applications of x-ray lasers among which was the interferometry of laser-produced and capillary discharge plasmas in several irradiation conditions for different target Z materials. The reduction of pump energy remains the most important for the generation of new compact x-ray lasers. Numerical studies show that there are some ways to improve several of the key parameters of x-ray lasers specifically repetition rates and efficiency.

Discharge-driven 46.9-nm amplifier with gain-length approaching saturation

Gain length products up to gl/spl ap/14 for the J=0-1 line of Ne-like Ar at 46.9 nm have been achieved in 15-cm-long plasma columns generated by a fast capillary discharge. Amplification in plasma columns up to 20 cm in length was investigated. The laser line intensity is observed to increase exponentially for plasma lengths of up to 15 cm, above which it is observed to saturate. The saturation behavior is discussed. >

Demonstration of a discharge pumped table-top soft X-ray laser

We report the first observation of large soft X-ray amplification (g*1=7.2) in a discharge created plasma. A fast, /spl sim/40 kA current pulse from a compact discharge was used to excite plasma columns up to 12 cm in length in 4 mm channels, producing population inversion in the J=0-1 line of Ne-like Ar and resulting in a gain of 0.6 cm/sup -1/ at 46.9 nm. The capillary discharge excitation scheme has the potential for increasing the wall-plug efficiency of ultrashort wavelength lasers by two orders of magnitude.

Research and development for X-ray optics and diagnostics on the linac coherent light source (LCLS)

The Linac Coherent Light Source (LCLS) is a 1.5 to 15 {angstrom} wavelength Free-Electron Laser (PEL), under development at the Stanford Linear Accelerator Center (SLAC). The photon output consists of high brightness, transversely coherent pulses with duration < 300 fs, together with a broad spontaneous spectrum. The output energy density per unit area, pulse duration, repetition rate, and small FEL spot size pose special challenges for optical components and diagnostics downstream of the undulator. Planning for the photon beam transport, manipulation and diagnostics downstream of the undulator has begun.

Refraction effects on x-ray and ultraviolet interferometric probing of laser-produced plasmas

We present a study detailing the effects of refraction on the analysis and interpretation of line-of-site optical probe characterization techniques within laser-produced plasmas. Results using x-ray laser backlit grid deflectometry and ray-tracing simulations illustrate the extent to which refraction can be a limiting factor in diagnosing high-density, short-scale-length plasmas. Analysis is applied to a recent experiment in which soft-x-ray interferometry was used to measure the electron density within a fast-evolving Al plasma. Comparisons are drawn between extreme ultraviolet and ultraviolet probe wavelengths.

Transient collisional excitation X-ray lasers with 1-ps tabletop drivers

Recent results are presented for 1-ps driven X-ray laser amplification in Ne-like and Ni-like transient collisional excitation research at the Lawrence Livermore National Laboratory. Plasma formation, ionization and collisional excitation are optimized using two laser pulses of 600- and 1-ps duration at tabletop energies of typically 5 J or less in each beam. Gain of 35 cm/sup -1/ and higher has been measured on the 147 /spl Aring/ 4d/spl rarr/4pJ=0/spl rarr/1 transition of Ni-like Pd and is a direct consequence of the nonstationary population in, version produced by the high intensity picosecond pulse. We report the characterization of the X-ray laser properties including the transient gain lifetime and beam divergence for different Ne-like and Ni-like X-ray lasers.

Shadowgrams of a dense micro-capillary plasma obtained with a table-top soft X-ray laser

A sequence of high resolution shadowgrams that map the evolution of the plasma of a 380 /spl mu/m diameter microcapillary discharge was obtained using a very compact 46.9 nm laser. These images are the first plasma diagnostics data obtained using a table-top soft X-ray laser.

High gain x-ray lasers pumped by transient collisional excitation

We present recent results of x-ray laser amplification of spontaneous emission in Ne-like and Ni-like transient collisional excitation schemes. The plasma formation, ionization and collisional excitation can be optimized using two laser pulses of 1 ns and 1 ps duration at table-top energies of 5 J in each beam. High gain of 35 cm{sup -1} has been measured on the 147 {Angstrom} 4d{r_arrow}4p J=0{r_arrow}1 transition of Ni-like Pd and is a direct consequence of the nonstationary population inversion produced by the high intensity picosecond pulse. We report the dependence of the x-ray laser line intensity on the laser plasma conditions and compare the experimental measurements with hydrodynamic and atomic kinetics simulations for Ne-like and Ni-like lasing.